The invention relates generally to electrically- and mechanically-interconnected flatwire segments.
In order to reduce vehicle weight while increasing the reliability of a vehicle""s electrical systems, the automotive industry is increasingly utilizing flexible flatwire busses extending between various electronic sites and/or systems in a vehicle. Each flatwire bus is preferably formed of a plurality of interconnected flatwire segments in order to afford greater flexibility in the assembly and customization of the vehicle""s electrical system while further capitalizing on an increased integration of such bus segments into other vehicle components, such as HVAC ducts, instrument panel structures, and the like.
In accordance with a known approach for interconnecting such flatwire segments, the segments are respectively outfitted with male and female connectors, whereupon the connectors are joined and locked together to complete the interconnection. Much attention has been focused on achieving a satisfactory electrical connection between the conductive traces of each flatwire segment and the corresponding connector tips. However, such use of electrical connectors along the length of the resulting flatwire bus may nonetheless degrade bus performance, while the weight and bulk of such electrical connectors continue to limit design flexibility and attendant gains in system integration.
It is an object of the invention to provide a flatwire assembly featuring a mechanical and electrical interconnection between a pair of flatwire segments, and an associated method for interconnecting the pair of flatwire segments, that overcomes the deficiencies of the prior art.
Under the invention, two flatwire segments are mechanically joined, and the respective conductive traces of the flatwire segments are electrically interconnected, by a flatwire jumper patch that is secured to the top face of the segments"" opposed longitudinal ends by a layer of a suitable adhesive. Conductive traces exposed on the top face of each flatwire segment are respectively electrically interconnected with corresponding conductive traces exposed on the bottom face of the patch by a solder layer.
At least one and, preferably, each solder layer extends generally longitudinally of the segment traces, out slightly beyond an edge of the patch overlying the respective flatwire segment. The edge of the patch overlying the respective flatwire segment is either a longitudinal end of the patch or, preferably, is an edge defined by a peripheral portion of an aperture or xe2x80x9cwindowxe2x80x9d defined in the patch. The solder layer extensions atop the segment traces permit a visual inspection of the resulting flatwire assembly, by which to confirm the successfully electrical interconnection between the respective traces of the patch and each flatwire segment.
In accordance with another aspect of the invention, the patch preferably includes a flexible substrate defining longitudinal extensions that overlie respective portions of each flatwire segment that are farther removed from the segment""s end than the visible solder layer extensions. Further, the flatwire assembly""s adhesive layer preferably extends between the patch substrate extensions and the corresponding portions of the flatwire segments such that, once the patch is bonded to the flatwire segments, the patch substrate extensions advantageously provide improved mechanical strain relief to the resulting flatwire assembly.
Also under the invention, a method is provided for interconnecting a pair of flatwire segments, each flatwire segment including a top face, a longitudinal end, and a plurality of conductive traces exposed on the top face proximate to the longitudinal end. The method includes positioning a patch directly atop the opposed ends of the flatwire segments, with the patch including a generally-flat, flexible substrate, a bottom face, a top face, a plurality of edges, a plurality of conductive traces exposed on the bottom face of the patch, and a solder layer formed on the traces of the patch.
The method also includes applying heat and pressure to a portion of the top face of the patch overlying the solder layer to thereby reflow the solder layer generally along the traces of the flatwire segments to a point slightly beyond a respective one of the edges of the patch, whereby at least one solder layer extension is formed on a given trace of each segment. The method further includes inspecting the solder layer extensions to confirm an electrical interconnection by the solder layer of the respective traces of the patch and the segments. The method preferably also includes covering the solder layer extensions with a protective layer after inspecting, as with a self-adhesive tape cover.
In accordance with another aspect of the invention, the method preferably includes preparing the patch by applying the solder layer to the traces of the patch, prior to position the patch atop the segment ends, either as a solder paste by stenciling or as solder plating. The ends of the segments are preferably prepared by applying a flux to the traces of the segments prior to positioning the patch.
In accordance with yet another aspect of the invention, the method preferably includes applying a layer of either a thermally-cured adhesive or a pressure-sensitive adhesive to a portion of the bottom face of the patch prior to positioning the patch atop the segment ends. By way of example only, in a preferred method, the adhesive is a thermoplastic adhesive having a curing temperature lower than the reflow temperature of the solder. The adhesive is thereby advantageously formed into a suitable adhesive layer and activated/cured during the step of applying heat and pressure to reflow the solder layer.
Additional features, benefits, and advantages of the invention will become apparent to those skilled in the art to which the invention relates from the subsequent description of several exemplary embodiments and the appended claims, taken in conjunction with the accompanying Drawings.